/**
 * Created with IntelliJ IDEA.
 * Description:
 * https://gitee.com/li--jiaqiang/java-test.git
 * git pull
 * git pull origin master
 * git pull origin master --allow-unrelated-histories
 * User: 86187
 * Date: 2022-04-27
 * Time: 22:21
 */

//Scanner scan = new Scanner(System.in);

import java.util.Scanner;

public class TestDemo3 {
    /**
     * 求单身狗数：有一组数据，只有一个数字是出现一次，其他是两次，请找出这个数字。
     * @param array
     * @return
     */
    public static int mySearch(int[] array) {
        int ans = 0;
        for (int i = 0; i < array.length; i++) {
            ans ^= array[i];
        }
        return ans;
    }

    public static void main(String[] args) {
        //int[] array = {1,3,5,5,4,3,1,4,9,7,6,7,6};
        int[] array = new int[11];
        Scanner scan = new Scanner(System.in);

        for (int i = 0; i < array.length; i++) {
            array[i] = scan.nextInt();
        }

        System.out.println(mySearch(array));
    }
}
